Bearing assembly having a slinger disk seal element

ABSTRACT

A bearing for a driving shaft of an electrical machine is lubricated by a lubricant. Located between the bearing and rotating parts arranged on the driving shaft is a seal element for lubricant emerging from the bearing. The seal element is configured in the form of a slinger disk by which lubricant emerging from the bearing is returned to the bearing, thus resulting in a closed lubricant circulation. The slinger disk is produced entirely from an elastic material. Lubricant sent off from the slinger disk is returned directly to the bearing.

BACKGROUND INFORMATION

The present invention relates to a bearing for use with an electricalmachine that includes a drive shaft mounted in a housing.

European Published Patent Application No. 698 956 describes a knownbearing in which a spherical cap, which is made of sintered material andwith which a repository for lubricant is associated in order tolubricate the bearing, is used to mount a driving shaft of an electricalmachine. Located between the spherical cap and the commutator is athrust washer or cover disk which consists of a first solid annular diskelement and a second elastic disk element joined positively thereto. Thesolid disk element has two peripheral slinger edges facing the sphericalcap. The sintered material used for the spherical cap has the propertythat because of the capillary effect of the interstices which arepresent, lubricant is stored and is delivered to the drive shaft duringoperation as a result of pressure differences. This results inlubrication of the driving shaft, so that it is mounted in alow-friction and low-wear manner in the spherical cap. Due to heating ofthe sintered bearing during operation of the electrical machine,however, an increase in the volume of the stored lubricant can occur, sothat it can emerge laterally out of the sintered bearing. This lubricantemerging during operation is thrown onto the bearing housing via theslinger edges, and returns from there to the spherical cap. Thisarrangement allows reliable sealing of the bearing even with largeassembly tolerances. The two-part configuration of the slinger disknevertheless requires increased manufacturing and assembly outlay.Moreover, without additional sealing measures it is impossible to ruleout completely the possibility that lubricant slung onto the housingwall may penetrate via the surrounding housing to the adjacentcommutator.

U.S. Pat. No. 4,711,590 discloses a bearing device for mounting thedriving shaft of an electrical machine, having a one-piece slinger diskmade of a solid material. The bearing arrangement as a whole isseparated by means of a housing from rotating parts arranged on thedriving shaft.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a bearing arrangementwhich is simple to manufacture and which reliably prevents lubricantfrom getting onto the rotating parts arranged on the driving shaft.

In order to achieve this object, the slinger disk of the presentinvention is made in one piece of an elastic material and can bemanufactured economically and easily even with complex geometries. Theflexibility of the slinger disk of the present invention facilitates theassembly thereof, so that the bearing as a whole is easy to assemble.Advantageously, a thermoplastic elastomer is used to manufacture theslinger disk.

It is particularly advantageous if the bearing is configured, toward theslinger disk, in such a way that any lubricant slung away by the slingerdisk is thrown directly back onto the bearing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a sectioned depiction through the bearing region of acontinuous excited direct-current motor;

FIG. 2 shows a sectioned depiction through a bearing;

FIG. 3 shows a sectioned depiction through a seal element;

FIG. 4 shows an enlarged detail view of the seal element of FIG. 3; and

FIG. 5 shows a plan view of the seal element.

DETAILED DESCRIPTION

FIG. 1 shows, in a sectioned depiction, the commutator-side bearingregion of a continuously excited direct-current motor 10. Direct-currentmotor 10 possesses a driving shaft 14, mounted within a housing 12,which carries a commutator 16 and a rotor 18. Driving shaft 14 ismounted in a sintered bearing 20. Sintered bearing 20 is arranged in arecess 22 of a bearing shell 24. Bearing shell 24 is immovably joined tohousing 12. Additional details of direct-current motor 10 will not bediscussed further in the context of the present description, since theconstruction and operation of a direct-current motor are commonly known.Only the parts essential for the invention will therefore be explainedin more detail below.

A seal element 26 is arranged immovably between sintered bearing 20 andcommutator 16 on driving shaft 14 so that seal element 26 co-rotates asdriving shaft 14 rotates. Seal element 26 is constituted by a slingerdisk 28. Slinger disk 28 consists entirely of an elastic material,preferably of a thermoplastic elastomer. Sintered bearing 20 is arrangedimmovably in recess 22 and is retained by a clamp 30. Clamp 30constitutes an attachment flange 32 which is attached by means of anattachment means 34 to bearing shell 24. Clamp 30 furthermoreconstitutes a receptacle 36 which rests against sintered bearing 20 andimmobilizes the latter in recess 22 of bearing shell 24. A section 38 ofclamp 30 joining attachment flange 32 to receptacle 36 is configured sothat there results between section 38 and bearing shell 24 a cavity 40which is filled with a lubricant 42 in the form of oil in an inorganicor organic thickener. Lubricant 42 serves as a source for lubricantstored in known fashion in sintered bearing 20. Because of the porosityof the sintered material of sintered bearing 20, a lubricant can bestockpiled there by impregnation, and is stored in sintered bearing 20as a result of a capillary effect.

The specific design of sintered bearing 20 and seal element 26 that isin accordance with the present invention will be explained in moredetail with reference to the following FIGS. 2 through 5.

As is evident from FIG. 2, sintered bearing 20 possesses a base element44 which is configured substantially cylindrically. Base element 44possesses a through opening 46 which serves to receive driving shaft 14.In this context, a diameter of through opening 46 correspondssubstantially to a diameter of driving shaft 14, so that the latter canbe mounted with a bearing clearance corresponding to the operatingconditions, for example temperature range, and the lubricant being used.External periphery 48 of base element 44 possesses flattened areas 52,extending along an imaginary circular line 50, whose contourcorresponding to circular line 50 is matched on the one hand to recess22 of bearing shell 24 and to receptacle 36 of clamp 30. Base element 44possesses, at least on its side facing commutator 16, an axialdepression 54 with a diameter d which is greater than a diameter ofthrough opening 46 but less than the diameter of base element 44 in theregion of flattened areas 52. As a result of depression 54, throughopening 46 is more or less divided, in the region of depression 54, intoa smaller-diameter section and a larger-diameter section, transitioningvia an annular step 56. In this context, driving shaft 14 is mountedexclusively in the smaller-diameter region of through opening 46. Thepresence of depression 54 thus results in the constitution of a space 58which is delimited by annular step 56, driving shaft 14, a peripheralsurface 60, depression 54, and seal element 26. A transition fromannular step 56 into peripheral surface 60 is accomplished preferablyvia a radius.

Slinger disk 28 is depicted in more detail in FIGS. 3 and 4, FIG. 3showing a sectioned depiction and FIG. 4 an enlarged partial view of thesectioned depiction. Slinger disk 28 consists of a concavely curved disk62 whose concavity faces in the direction of sintered bearing 20. Disk62 consists entirely of an elastic material which is selected so as todamp impact noises generated by sintered bearing 20 striking againstslinger 28 when driving shaft 14 is axially excited. Slinger disk 28lies against driving shaft 14 with an elastic press fit, thusadditionally preventing oil from migrating along driving shaft 14. Disk62 has an external ridge 64 and an internal ridge 66. Internal ridge 66surrounds a through opening 68 whose diameter corresponds to thediameter of driving shaft 14. A peripheral surface 70 of through opening68 possesses an annular groove 72 which constitutes a sealing fit withdriving shaft 14. Internal ridge 66 possesses, on its outer peripheralsurface 74, a further annular groove 76 which is constituted by a radialsurface 77 of an axially reentrant edge 78 and an edge 82 projectingoutward at an angle α to an axis 80. The axial dimension c of edgereentrant 78 is selected to be greater than the axial dimension b ofedge 82, thus resulting in a lug-shaped projection 86 which runsannularly and extends into cavity 84 encompassed by periphery 62 ofslinger disk 28. A diameter d₁ of peripheral surface 74 is smaller thandiameter d₂ of depression 54 of sintered bearing 20.

It is clear from the plan view of slinger disk 28 shown in FIG. 5 thatannular groove 76 completely surrounds through opening 68. In thiscontext, reentrant edge 78 of annular groove 76 is arranged at adistance from through opening 68, thus resulting in a radially extendingannular surface 88. Because of the configuration of edges 78 and 82,annular surface 88 extends at an axial distance c from projection 86.Distance c is selected to be less than a depth t of depression 54 ofsintered bearing 20 (FIG. 2).

During the assembly of direct-current motor 10, slinger disk 28 is slid,with a corresponding undersize with respect to driving shaft 14, ontodriving shaft 14 until it rests against commutator 16. Annular surface88 of slinger disk 28 rests against annular step 56 of sintered bearing20. The result is that annular groove 76 extends within space 58, suchthat projection 86 ends in space 58 and is at a distance a from annularstep 56.

While direct-current motor 10, which for example can serve as the drivemotor of a cooling and climate-control fan, is being used as intended,driving shaft 14 and rotor 18, commutator 16, and slinger disk 28attached thereon rotate in accordance with the rotation speed of drivingshaft 14. Driving shaft 14 simultaneously rotates within sinteredbearing 20; because of lubricant 42 stored in sintered bearing 20, alubricant film is produced between sintered bearing 20 and driving shaft14, resulting in low-friction mounting of driving shaft 14. During theoperation of direct-current motor 10, heating of sintered bearing 20 mayoccur as a result of internal or external influences that will not bediscussed here in further detail. As a result, the stored lubricant 42experiences an increase in volume that can be, for example, 10 to 15%.Because of this increase in volume, the lubricant 42 emerges, amongother directions, axially from sintered bearing 20 and encountersslinger disk 28. Because slinger disk 28 rests in sealed fashion againstdriving shaft 14, the sealing effect being enhanced by annular groove 72in peripheral surface 70 resting on driving shaft 14, the emerginglubricant 42 cannot move past slinger disk 28 in the direction ofcommutator 16. The emerging lubricant 42 passes through the contact seatcreated by annular step 56 of sintered bearing 20 and annular surface 88of slinger disk 28, and migrates toward space 58. There it migratesalong axially reentrant edge 78 into annular groove 76. The emerginglubricant 42 is retained in annular groove 76 as a result of thecapillary effect. As the amount of lubricant 42 emerging axially fromsintered bearing 20 steadily increases, edge 82 projecting outward at anangle constitutes a flow barrier, so that annular groove 76 becomesincreasingly filled with lubricant 42 up to a maximum. When thereceiving capacity of annular groove 76 is exceeded, lubricant 42 isslung off via projection 86 as a result of the centrifugal forcesoccurring due to the rotation of slinger disk 28. Depending on theselection of angle, which is preferably 45°, lubricant 42 is slung offinto space 58. Since distance c is less than depth t, within space 58lubricant 42 encounters annular step 56 or peripheral surface 60 ofdepression 54. As a result of the capillary effect of the sinteredmaterial of sintered bearing 20, the lubricant 42 striking base element44 of sintered bearing 20 can be taken up again by sintered bearing 20and reused to lubricate sintered bearing 20. The overall result is thusa closed lubricant circulation which prevents lubricant 42 from emergingbeyond sintered bearing 20 or cavity 84 enclosed by disk 62. This on theone hand prevents any contamination of the interior of housing 12 ofdirect-current motor 10, and the lubricant supply of sintered bearing 20is always being topped up, so that overall, maintenance-free operationis possible. Any impairment of the electrical functionality ofdirect-current motor 10 due to the formation of a carbonized lubricantpaste on commutator 16 is also prevented.

As a feature which is not absolutely necessary for the closed lubricantcirculation according to the present invention, FIG. 4 shows the elasticslinger disk 28 as possessing on its external ridge 64 a further annulargroove 90, open radially toward driving shaft 14, which serves as asafety collector for any lubricant 42 that might still, due to extremeoperating situations, manage to get out of space 58. In such a caselubricant 42 is reliably prevented from entering the interior ofdirect-current motor 10.

The present invention is of course not limited to the exemplaryembodiment depicted. For example, the combination according to theinvention of sintered bearing 20 with the present elastic slinger disk28 may also be utilized in any other bearing to achieve the closedlubricant circulation. In particular, any other bearing lubricated 42with lubricant may also be provided instead of a sintered bearing 20which stores lubricant. The applications of the bearing are also notlimited to electrical machines.

What is claimed is:
 1. A bearing assembly for guiding a driving shaft ofan electrical machine having rotating parts arranged on the drivingshaft, comprising:a bearing lubricated by a lubricant; and a lubricantseal element arranged between the bearing and the rotating parts andbeing formed as a slinger disk made of an elastic materials, wherein:theslinger disk and the bearing form a closed lubricant circulation throughwhich the lubricant emerging from the bearing is returned to thebearing, the lubricant emerging from the bearing is returned directly tothe bearing via the slinger disk, the slinger disk has an annular groovein which the lubricant is collected, the annular groove is formed by aradial surface of an axially reentrant edge of the slinger disk and asecond edge of the slinger disk that projects outward at a predeterminedangle from said radial surface of said axially reentrant edge, saidaxially reentrant edge has an axial dimension that is greater in lengththan an axial dimension of the second edge, and the second edge forms anannular projection which ends at a predetermined distance from a radialannular surface of the slinger disk from which the axially reentrantedge is formed.
 2. The bearing assembly according to claim 1, whereinthe bearing includes an axial depression arranged on a side of thebearing facing the lubricant seal element and into which the lubricantseal element at least partly engages.
 3. The bearing assembly accordingto claim 2, wherein a diameter of the axial depression is greater than adiameter of the annular projection.
 4. The bearing assembly according toclaim 2, wherein a depth of the axial depression is greater than thepredetermined distance, and wherein the annular groove and the annularprojection are arranged inside the axial depression.
 5. A bearingassembly for guiding a driving shaft of an electrical machine havingrotating parts arranged on the driving shaft, comprising:a bearinglubricated by a lubricant; and a lubricant seal element arranged betweenthe bearing and the rotating parts and being formed as a slinger disk bywhich the lubricant emerging from the bearing is retained, the slingerdisk being made of an elastic material and having an annular groove inwhich the lubricant is collected, wherein:the annular groove includes anannular projection located at a distance from a radial annular surfaceof the slinger disk, a side of the bearing facing the slinger diskincludes an axial recess having a depth, and the depth of the axialrecess is greater than the distance of the annular projection from theradial annular surface such that the annular projection is locatedinside the axial recess.
 6. The bearing assembly according to claim 5,wherein the annular groove is formed by an axially reentrant edge of theslinger disk and a second edge of the slinger disk that projects outwardat a predetermined angle from a surface of the axially reentrant edge.